package org.bouncycastle.crypto.engines;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.StreamCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

HC-128 is a software-efficient stream cipher created by Hongjun Wu. It generates keystream from a 128-bit secret key and a 128-bit initialization vector.

http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf

It is a third phase candidate in the eStream contest, and is patent-free. No attacks are known as of today (April 2007). See http://www.ecrypt.eu.org/stream/hcp3.html

/** * HC-128 is a software-efficient stream cipher created by Hongjun Wu. It * generates keystream from a 128-bit secret key and a 128-bit initialization * vector. * <p> * http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf * </p><p> * It is a third phase candidate in the eStream contest, and is patent-free. * No attacks are known as of today (April 2007). See * * http://www.ecrypt.eu.org/stream/hcp3.html * </p> */
public class HC128Engine implements StreamCipher { private int[] p = new int[512]; private int[] q = new int[512]; private int cnt = 0; private static int f1(int x) { return rotateRight(x, 7) ^ rotateRight(x, 18) ^ (x >>> 3); } private static int f2(int x) { return rotateRight(x, 17) ^ rotateRight(x, 19) ^ (x >>> 10); } private int g1(int x, int y, int z) { return (rotateRight(x, 10) ^ rotateRight(z, 23)) + rotateRight(y, 8); } private int g2(int x, int y, int z) { return (rotateLeft(x, 10) ^ rotateLeft(z, 23)) + rotateLeft(y, 8); } private static int rotateLeft( int x, int bits) { return (x << bits) | (x >>> -bits); } private static int rotateRight( int x, int bits) { return (x >>> bits) | (x << -bits); } private int h1(int x) { return q[x & 0xFF] + q[((x >> 16) & 0xFF) + 256]; } private int h2(int x) { return p[x & 0xFF] + p[((x >> 16) & 0xFF) + 256]; } private static int mod1024(int x) { return x & 0x3FF; } private static int mod512(int x) { return x & 0x1FF; } private static int dim(int x, int y) { return mod512(x - y); } private int step() { int j = mod512(cnt); int ret; if (cnt < 512) { p[j] += g1(p[dim(j, 3)], p[dim(j, 10)], p[dim(j, 511)]); ret = h1(p[dim(j, 12)]) ^ p[j]; } else { q[j] += g2(q[dim(j, 3)], q[dim(j, 10)], q[dim(j, 511)]); ret = h2(q[dim(j, 12)]) ^ q[j]; } cnt = mod1024(cnt + 1); return ret; } private byte[] key, iv; private boolean initialised; private void init() { if (key.length != 16) { throw new java.lang.IllegalArgumentException( "The key must be 128 bits long"); } cnt = 0; int[] w = new int[1280]; for (int i = 0; i < 16; i++) { w[i >> 2] |= (key[i] & 0xff) << (8 * (i & 0x3)); } System.arraycopy(w, 0, w, 4, 4); for (int i = 0; i < iv.length && i < 16; i++) { w[(i >> 2) + 8] |= (iv[i] & 0xff) << (8 * (i & 0x3)); } System.arraycopy(w, 8, w, 12, 4); for (int i = 16; i < 1280; i++) { w[i] = f2(w[i - 2]) + w[i - 7] + f1(w[i - 15]) + w[i - 16] + i; } System.arraycopy(w, 256, p, 0, 512); System.arraycopy(w, 768, q, 0, 512); for (int i = 0; i < 512; i++) { p[i] = step(); } for (int i = 0; i < 512; i++) { q[i] = step(); } cnt = 0; } public String getAlgorithmName() { return "HC-128"; }
Initialise a HC-128 cipher.
Params:
  • forEncryption – whether or not we are for encryption. Irrelevant, as encryption and decryption are the same.
  • params – the parameters required to set up the cipher.
Throws:
/** * Initialise a HC-128 cipher. * * @param forEncryption whether or not we are for encryption. Irrelevant, as * encryption and decryption are the same. * @param params the parameters required to set up the cipher. * @throws IllegalArgumentException if the params argument is * inappropriate (ie. the key is not 128 bit long). */
public void init(boolean forEncryption, CipherParameters params) throws IllegalArgumentException { CipherParameters keyParam = params; if (params instanceof ParametersWithIV) { iv = ((ParametersWithIV)params).getIV(); keyParam = ((ParametersWithIV)params).getParameters(); } else { iv = new byte[0]; } if (keyParam instanceof KeyParameter) { key = ((KeyParameter)keyParam).getKey(); init(); } else { throw new IllegalArgumentException( "Invalid parameter passed to HC128 init - " + params.getClass().getName()); } initialised = true; } private byte[] buf = new byte[4]; private int idx = 0; private byte getByte() { if (idx == 0) { int step = step(); buf[0] = (byte)(step & 0xFF); step >>= 8; buf[1] = (byte)(step & 0xFF); step >>= 8; buf[2] = (byte)(step & 0xFF); step >>= 8; buf[3] = (byte)(step & 0xFF); } byte ret = buf[idx]; idx = idx + 1 & 0x3; return ret; } public void processBytes(byte[] in, int inOff, int len, byte[] out, int outOff) throws DataLengthException { if (!initialised) { throw new IllegalStateException(getAlgorithmName() + " not initialised"); } if ((inOff + len) > in.length) { throw new DataLengthException("input buffer too short"); } if ((outOff + len) > out.length) { throw new DataLengthException("output buffer too short"); } for (int i = 0; i < len; i++) { out[outOff + i] = (byte)(in[inOff + i] ^ getByte()); } } public void reset() { idx = 0; init(); } public byte returnByte(byte in) { return (byte)(in ^ getByte()); } }